U.S. patent number 4,611,558 [Application Number 06/778,304] was granted by the patent office on 1986-09-16 for valve actuating apparatus in internal combustion engine.
This patent grant is currently assigned to Toyota Jidosha Kabushiki Kaisha. Invention is credited to Toshio Tanahashi, Kouji Yoshizaki.
United States Patent |
4,611,558 |
Yoshizaki , et al. |
September 16, 1986 |
Valve actuating apparatus in internal combustion engine
Abstract
A valve actuating apparatus for intake and exhaust valves in an
internal combustion engine having a swing rocker arm consisting of
two arms rotatably interconnected by means of a connecting shaft,
one of the arms being rotatably connected to a rocker arm shaft and
the other bearing against a valve stem so that the two arms can
selectively occupy an operative position, in which the two arms
extend substantially straight to form a single rocker arm, and an
inoperative position in which a relative rotation between the two
arms takes place to absorb the rotation of the cam. A lock pin is
provided in one of the first and second arms to prevent relative
rotation of the two arms and to lock them to the operative
position, and an actuator for releasing the lock at a predetermined
time, the locking means and unlocking means having directions of
operation substantially perpendicular to and across the axis of the
connecting shaft.
Inventors: |
Yoshizaki; Kouji (Susono,
JP), Tanahashi; Toshio (Susono, JP) |
Assignee: |
Toyota Jidosha Kabushiki Kaisha
(Aichi, JP)
|
Family
ID: |
27454274 |
Appl.
No.: |
06/778,304 |
Filed: |
September 20, 1985 |
Foreign Application Priority Data
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Oct 12, 1984 [JP] |
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59-153107[U] |
Jan 21, 1985 [JP] |
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60-5319[U]JPX |
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Current U.S.
Class: |
123/90.16;
123/198F; 123/90.27; 123/90.39; 123/90.44 |
Current CPC
Class: |
F01L
13/0005 (20130101); F01L 1/185 (20130101) |
Current International
Class: |
F01L
13/00 (20060101); F01L 1/18 (20060101); F02D
013/06 () |
Field of
Search: |
;123/90.15,90.16,90.27,90.39,90.44,198F |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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57-193903 |
|
Dec 1982 |
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JP |
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57-193904 |
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Dec 1982 |
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JP |
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59-68109 |
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May 1984 |
|
JP |
|
59-67506 |
|
May 1984 |
|
JP |
|
P59-226216 |
|
Dec 1984 |
|
JP |
|
Primary Examiner: Lazarus; Ira S.
Attorney, Agent or Firm: Parkhurst & Oliff
Claims
We claim:
1. A valve actuating apparatus for intake and exhaust valves in an
internal combustion engine having a swing rocker arm which is
rotatably connected at its one end to a rocker arm shaft and at its
opposite end bears against a valve stem of an associated intake or
exhaust valve, and a rotatable cam which bears against the swing
rocker arm to swing the latter about the rocker arm shaft, wherein
said rocker arm is composed of a first arm which is rotatably
connected to the rocker arm shaft and a second arm which bears
against the valve stem and which is connected to the first arm by
means of a connecting shaft extending in parallel to the rocker arm
shaft, for relative rotation about the connecting shaft so that the
two arms can selectively occupy an operative position in which the
two arms are integral with each other and extend substantially
straight so as to form a single rocker arm, and an inoperative
position in which a relative rotation between the two arms takes
place to absorb the rotation of the cam, and wherein said apparatus
comprises locking means for preventing the relative rotation of the
two arms to lock them to the operative position, unlocking means
for releasing the lock at a predetermined time, and return means
for continuously biasing the two arms toward the operative position
to return them to the operative position when the lock is released,
said locking means and unlocking means having directions of
operation substantially perpendicular to and across the axis of the
connecting shaft.
2. An apparatus according to claim 1, wherein said locking means
comprises a lock pin which is slidably inserted in a pin hole
provided in one of the first and second arms to receive the lock
pin for sliding movement, and a recess provided in the other of the
first and second arms to receive the lock pin in part only when the
two arms are locked.
3. An apparatus according to claim 2, wherein said return means
comprises at least one return spring which continuously biases one
of the first and second arms toward the operative position.
4. An apparatus according to claim 2, wherein said unlocking means
comprises a hydraulic actuator comprising a cylinder and a piston
slidable therein to actuate the lock pin.
5. An apparatus according to claim 4, wherein said first and second
arms are brought into surface contact with each other by a arcuated
contact surface along which relative rotation takes place between
the first and second rotation, and wherein said piston and said
lock pin normally come into contact with each other at the arcuated
contact surface.
6. An apparatus according to claim 4, further comprising a spring
means for continuously biasing the lock pin toward the piston.
7. An apparatus according to claim 1, wherein said locking means
and said unlocking means comprise a common lock pin provided in one
of the first and second arms, a common hydraulic actuator for
actuating the lock pin, and a recess provided in the other of the
first and second arms for disengageably receiving the lock pin,
said lock pin being continuously biased toward the inoperative
position.
8. An apparatus according to claim 7, wherein said hydraulic
actuator comprises a cylinder provided in said one of the first and
second arms and wherein said lock pin is slidably inserted in the
cylinder to actuate the lock pin when the two arms are locked.
9. An apparatus according to claim 4, wherein said cylinder has a
stepped cylinder bore consisting of a large bore opening to the
atmosphere and a smaller bore coaxial to the large bore, and
wherein said recess for receiving the lock pin is coaxial to the
smaller bore and has the same diameter as the smaller bore, so that
the cylinder bore and the recess can be formed at one time from the
side of the large bore of the cylinder bore.
10. An apparatus according to claim 8, wherein said cylinder has a
stepped cylinder bore consisting of a large bore opening to the
atmosphere and a smaller bore coaxial to the large bore, and
wherein said recess for receiving the lock pin is coaxial to the
smaller bore and has the same diameter as the smaller bore, so that
the cylinder bore and the recess can be formed at one time from the
side of the large bore of the cylinder bore.
11. An apparatus according to claim 2, further comprising air
escape means for discharging the air confined in said recess into
the atmosphere.
12. An apparatus according to claim 11, wherein said air escape
means comprises an air passage provided in and extending through
the lock pin.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a valve actuating apparatus for
intake and exhaust valves in an internal combustion engine. More
particularly, it relates to a valve actuating apparatus which can
render only a predetermined intake and/or exhaust valve or valves
inoperative at a given engine condition.
2. Description of the Related Art
In a multi-cylinder internal combustion engine, it is known to
selectively render only predetermined intake or exhaust valve(s)
inoperative in order to cancel out the associated cylinder(s),
thereby controlling the total displacement of the effective
cylinders, in accordance with the engine load, resulting in the
realization of a variable-cylinder internal combustion engine.
Among known valve actuating apparatuses of the kind mentioned
above, those closest to the present invention are disclosed, for
example, in Japanese Unexamined Utility Model Publication (Kokai)
Nos. 59-68109 and 59-67506, in which a rocker arm is divided into
two rocker arm elements, one of which bears against a cam and the
other bears against a valve stem of the associated intake or
exhaust valve. These two arms are interconnected for relative
sliding rotation. The relative sliding rotation takes place between
the two arms when only a predetermined intake or exhaust valve is
made temporarily inoperative, to absorb the valve lift of the
associated valve. The two arms are provided with male and female
engaging members which are selectively engaged and disengaged. One
of the male and female members can be actuated by an actuator, such
as solenoid means to selectively occupy locked and unlocked
positions.
However, in the known apparatuses mentioned above, the actuator
acts on the male or female member in a direction parallel to the
axis of the rocker arm shaft on which the rocker arm is supported,
namely in a direction in which the two arm elements tend to
separate and, accordingly, the two arm elements originally brought
into surface contact are forced to separate from one another. This
results in deviation of the arm elements from the respective
initial positions or undesirable displacement of the contact
portion of the second arm element that bears against the valve
stem.
SUMMARY OF THE INVENTION
The primary object of the present invention is, therefore, to
provide a simple valve actuating apparatus having so-called swing
type (end pivot type) two divided rocker arms which is free from
the aforementioned drawbacks and which can selectively cancel out
the operation of the desired intake or exhaust valve(s) without
deviation of the rocker arm and displacement of the portion of the
rocker arm in contact with the valve stem.
To achieve the object mentioned above, according to the present
invention there is provided a valve actuating apparatus for intake
and exhaust valves in an internal combustion engine having a swing
rocker arm which is rotatably connected at one end to a rocker arm
shaft and at its opposite end bears against a valve stem of an
associated intake or exhaust valve, and a rotatable cam which bears
against the swing rocker arm to swing the latter about the rocker
arm shaft, wherein said rocker arm is composed of a first arm
rotatably connected to the rocker arm shaft and a second arm which
bears against the valve stem and which is connected to the first
arm by means of a connecting shaft extending parallel to the rocker
arm shaft, for relative rotation about the connecting shaft, so
that the two arms can selectively occupy an operative position in
which the two arms are integral with each other and extend
substantially straight so as to form a single rocker arm, and an
inoperative position in which a relative rotation between the two
arms takes place to absorb the rotation of the cam, and wherein the
apparatus comprises locking means between the first and second arms
for preventing the relative rotation of the two arms to lock them
to the operative position, unlocking means between the first and
second arms for releasing the lock at a predetermined time, and
return means for continuously biasing the two arms toward the
operative position to return them to the operative position when
the lock is released, these locking means and unlocking means
having directions of operation substantially perpendicular to and
across the axis of the connecting shaft.
Other features and objects of the invention will become apparent
from the description given below.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described below in detail with reference to
the accompanying drawings, which show preferred embodiments of the
present invention, and in which:
FIG. 1 is a partially sectioned schematic view of a valve actuating
apparatus shown in an unlocked, i.e., inoperative position,
according to the present invention;
FIG. 2 is an enlarged plan view of a main part of FIG. 1;
FIG. 3 is a view similar to FIG. 1 but shown in a locked, i.e.,
operative, position when the valve is in a closed position;
FIG. 4 is a view similar to FIG. 3 but with the valve in an open
position;
FIG. 5 is a view similar to FIG. 2 according to a second embodiment
of the present invention;
FIG. 6 is a sectional view of a valve actuating apparatus shown in
a locked position, taken along the line VI--VI in FIG. 7, according
to a third embodiment of the present invention;
FIG. 7 is a plan view of FIG. 6;
FIG. 8 is a view similar to FIG. 6 but shown in an unlocked
position;
FIG. 9 is a sectional view of a valve actuating apparatus taken
along the line IX--IX in FIG. 11, according to the fourth
embodiment of the present invention;
FIG. 10 is a side elevational view of a main part of the apparatus
shown in FIG. 9; and,
FIG. 11 is a plan view of FIG. 10.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1 to 4 show a first embodiment of the invention, in which a
rocker arm 11 consists of two arms, i.e., a first arm 13A which is
rotatably connected to a rocker arm shaft 19, and a second arm 13B
which is connected to the first arm for relative rotation by means
of a connecting shaft 15 and which bears against a top end of a
valve stem 21 of an intake or exhaust valve (not shown). This type
of rocker arm is known as a swing type or end pivot type, in which
the first arm 13A is swingably pivoted to the rocker arm shaft 19.
The connecting shaft 15 extends in a direction parallel to the axis
of the rocker arm shaft 19 and, accordingly, a cam shaft 25, to
which a cam 23 is connected so as to rotate therewith.
As is well known, the cam shaft 25 is synchronously rotated by a
crank-shaft (not shown) to rotate the cam 23 connected thereon. The
cam 23 bears against the rocker arm 11 at an intermediate portion
of the latter to actuate the rocker arm. In the illustrated
embodiment, the cam 23 bears against the first arm 13A in the
vicinity of the front end of the first arm. It is also possible to
bring the cam 23 into contact with the second arm 13B at the
intermediate or rear portion thereof.
The connecting shaft 15 extends through the first and second arms
13A and 13B, which are connected side face to side face for
relative sliding rotation about the shaft 15, as can be seen from
FIG. 2. The rocker arm 11 can occupy two positions, i.e., an
operative position shown in FIGS. 3 and 4 and an inoperative
position shown in FIG. 1. In the operative position, the first and
second arms 13A and 13B are integral with each other, so that no
relative rotation can take place. Namely, the first and second arms
13A and 13B are then equivalent to a conventional single rocker
arm, when in the operative position, i.e., locked position as shown
in FIGS. 3 and 4.
On the other hand, the first and second arms 13A and 13B can rotate
relative to each other when they are in the inoperative position
shown in FIG. 1. In the illustrated embodiment, the second arm 13B
rotates about the connecting shaft 15 relative to the first arm
13A, so that when the rocker arm 11 is actuated by the cam 23, the
first and second arms 13A and 13B are brought into an inclined
position in which the second arm 13B largely rotates about the
shaft 15 relative to the first arm 13A. In FIGS. 1 and 3, the
numerals 12 and 14 designate a retainer mounted to the valve stem
21 and a return spring for the valve, respectively.
Between the first and second arms 13A and 13B, is provided a return
spring 29 which returns the rocker arm 11, which is located in the
inclined position by the cam 23, to the operative position shown in
FIGS. 3 and 4 (in which the two arms 13A and 13B extend
substantially straight as a single rocker arm) when a cam lobe 24
of the cam 23 separates from the rocker arm 11 during the rotation
of the cam 23.
The return spring 29 is made, for example, of a leaf spring
connected at one end to a pin 32 provided on the first arm 13A and
bearing at the opposite end against a pin 34 provided on the second
arm 13B. The return spring is not limited to such a leaf spring and
can be a coil spring or the like.
The first and second arms 13A and 13B come into surface contact
with each other at a contact surface 38 thereof for relative
sliding rotation, as mentioned before. They also are in contact
with each other at a curved contact surface 36, which has a radius
of curvature substantially identical to an arc of a circle along
which the rear end face of the second arm 13B rotates about the
shaft 15, so that the second arm 13B can rotate about the shaft 15
while sliding on the curved contact surface 36 of the first arm
13A.
A locking device for preventing the relative rotation of the first
and second arms 13A and 13B is provided between the two arms. The
locking device is composed of a lock pin 45, which is slidably
inserted in a blind hole 41 formed in the second arm 13B by means
of a spring 43. The lock pin 45 can be, for example, a movable
piston having a generally U-shape section, as shown in FIG. 2. The
lock pin 45 is completely retracted in the blind hole 41, which
forms a cylinder for the piston 45, in the inoperative position
mentioned above. This corresponds to the unlocked position, in
which the first and second arms 13A and 13B can rotate relative to
each other about the shaft 15.
The lock pin 45 is actuated by an actuator, which is comprised of a
piston 33 slidably fitted in a cylinder 31 formed in the first arm
13A. The piston 33 is opposed to the lock pin 45, that is, the
piston 33 is located in alignment with the lock pin 45, so that the
piston 33 bears against one end of the lock pin 45 at the contact
surface 36 between the first and second arms when the rocker arm 11
is in the inoperative position, i.e., when the lock pin 45 is in
the unlocked position. In this manner, the second arm 13B can
rotate about the shaft 15 relative to the first arm 13A in the
unlocked position.
The cylinder 31 is hydraulically connected to a bore 20 of the
hollow rocker arm shaft 19 through an oil passage 16 formed in the
first arm 13A. The bore 20 of the rocker arm shaft 19 is
hydraulically connected to an oil supply unit 50 having an oil pump
P, etc., through a switching valve 60, which selectively cuts the
supply of the pressurized oil to the bore 20. Namely, the switching
valve 60 operates in response to, for example, a signal S
representing an engine load, to feed the pressurized oil from the
oil unit 50 to the rocker arm shaft or to return the pressurized
oil to a drain. The switching valve can be, for example, a
conventional electromagnetic two-way valve, known per se.
A working fluid other than oil, such as air, water, etc, can be
utilized.
When the lock pin 45 is in the locked position, the pressurized oil
in the bore 20 is released, and accordingly, the lock pin 45 is
pushed by the spring 43 to push the piston 33 into the cylinder 31,
so that the lock pin 45 enters a recess 48 coaxial to the cylinder
31 formed in the first arm 13A. As a result of the entrance of the
lock pin 45 into the recess 48, the lock pin 45 renders the first
and second arms 13A and 13B integral, so that relative rotation can
no longer take place between the first and second arms. Namely, the
two arms are locked.
It will be appreciated that the piston 33 has a shoulder 33a which
prevents the front end of the piston 33 from projecting outward
from the contact surface 36 toward the lock pin 45, when the piston
33 is pushed by the pressurized oil in the cylinder 31 toward the
lock pin 45.
According to an aspect of the present invention, the lock pin 45,
the blind hole 41 receiving the lock pin, the cylinder 31, and the
piston 33 all extend in the same direction X--X (FIG. 3)
perpendicular to the axis Y--Y (FIG. 2) of the connecting shaft 15.
Namely, the direction of movement of the lock pin 45 and the piston
33, i.e., the direction of action of the force is perpendicularly
across the longitudinal axis of the shaft 15. With this
arrangement, since the force is exerted on the lock pin 45 or
piston 33 in the direction perpendicular to the axis of the shaft
15, both when the rocker arm 11 is locked and when it is unlocked,
a force causing the first and second arms 13A and 13B to separate
from one another is not exerted on the two arms.
The apparatus of the present invention operates as follows. First,
in the lock position of the lock pin 45, i.e., in the operative
position of the rocker arm 11, shown in FIGS. 3 and 4, the cylinder
31 is released from the pressurized oil and accordingly, lock pin
45 forces the piston 33 into the cylinder and partially enters the
recess 48, as mentioned before. Therefore, the two arms 13A and 13B
are integral with each other and, accordingly, the rocker arm 11
operates in the same fashion as the conventional single rocker arm.
Namely, when the intake or exhaust valve (not shown) is made open,
the cam lobe 24 of the cam 23 causes the valve stem 21 to move
downward in accordance with the cam lift, by means of the rocker
arm 11, as shown in FIG. 4, to open the associated valve. When the
cam lobe 24 comes away from the rocker arm 11 during the rotation
of the cam, the valve stem 21 is moved upwards by the spring 14 to
close the associated valve.
When, for example, it is desired to make a predetermined intake or
exhaust valve inoperative at a predetermined engine load, the
pressurized oil is fed to the cylinder 31 from the oil supply unit
50, so that the piston 33 forces the lock pin 45 into the blind
hole 41 against the spring 43 to release the lock. Thus, the rocker
arm 11 is unlocked, and the two arms 13A and 13B of the rocker arm
11 can rotate relative to each other. Accordingly, when the rocker
arm 11 is pushed down by the cam lobe 24, the second arm 13B
rotates about the shaft 15 and is inclined relative to the first
arm 13A to absorb the cam lift of the cam 23. In this manner, in
spite of continuation of the rotation of the cam 23, the cam effect
is cancelled out and is not transmitted to the valve stem 21, so
that the associated intake or exhaust valve remains inoperative,
i.e., remains closed. It should be noted that when the rocker arm
11 is in the unlocked position shown in FIG. 1, the lock pin 45
separates from the piston 33, but is still kept in an unlocked
state by the curved contact surface 36 of the first arm 13A. The
rocker arm 11 can be returned to the straight position identical to
the operative position, in which the two arms 13A and 13B extend
substantially straight, by means of the return spring 29 every time
the cam lobe 24 comes away from the rocker arm 11.
FIG. 5 shows another embodiment of the present invention. The
arrangement shown in FIG. 5 is different from that of the first
embodiment shown in FIGS. 1 to 4 mainly in the location of the lock
pin 45'. Namely, the lock pin 45' in the second embodiment shown in
FIG. 5 is provided in the first arm 13A. The lock pin 45' is
slidably located in the cylinder 31, which is formed in the first
arm 13A, so that the lock pin 45' is continuously biased toward the
unlocked position by means of the return spring 43'. The second arm
13B is provided with a blind hole 70 in which the lock pin 45'
enters when the rocker arm 11 is locked. The hole 70 is opposed to
the lock pin 45' in the cylinder 31, so that the lock pin 45', when
pushed by the pressurized oil fed in the cylinder 31 against the
spring 43', comes into the hole 70 to render the two arms 13A and
13B integral with each other. Since the lock pin 45' proper also
fulfills the role of the piston 33 illustrated in FIG. 2, a
particular actuator, such as the piston 33 can be dispensed with in
the embodiment shown in FIG. 5.
Note that the operation of the apparatus illustrated in FIG. 5 is
the same as that of the first embodiment except that the
pressurized oil is supplied to the cylinder 31 from the oil supply
unit 50 when the lock pin 45' is brought into the locked position,
contrary to the first embodiment.
Although not illustrated, the lock pin 45 or 45' can be actuated by
a mechanical means, such as a flexible wire or wire cable commonly
used in a release mechanism in a camera, in place of the hydraulic
actuator as shown in the aforementioned embodiments. In addition to
foregoing, it is also possible to actuate the lock pin 45 or 45' by
means of an electrical actuator, such as a solenoid means, or a
vacuum actuator, such as a diaphragm means. These actuators can be
then driven, for example, in accordance with an engine load.
As can be understood from the above discussion, according to the
present invention, in a valve actuating apparatus having a
so-called swing type or end pivot type rocker arm in which the
rocker arm is rotatably connected at one end to the rocker arm
shaft, bears at the opposite end against the valve stem, and bears
at the intermediate portion against the cam to swing about the
rocker arm shaft, a prodetermined valve or valves only can be
easily and assuredly rendered inoperative.
Further, according to the present invention, since the locking and
unlocking means act in the direction perpendicular to the axis of
the connecting shaft, which rotatably connects the two arms of the
rocker arm, no external force is exerted on the two arms to
separate or expand them, thus preventing deviation of the rocker
arm or displacement of the contacting portion between the rocker
arm and the valve stem. Furthermore, according to the present
invention, the width of the rocker arm in the direction parallel to
the axis of the connecting shaft can be decreased in comparison
with the prior art.
FIGS. 6 to 8 show another embodiment of the present invention, in
which the construction of the apparatus is simplified in comparison
with the aforementioned embodiments.
In the arrangement illustrated in FIGS. 6 to 8, the second arm 13B
is slidably and rotatably held in a bifurcated end 113 (FIG. 7) of
the first arm 13A. Note that the arrangements shown in FIGS. 6 and
8 are viewed as a reverse of the arrangements of FIGS. 1 and 3. In
FIG. 7, the return spring 29 in FIGS. 1 to 5 is replaced by a coil
return spring 29'. The coil spring 29' bears against the first arm
13A at one end and the second arm at the opposite end,
respectively.
The lock pin 45 is slidably inserted in a stepped cylinder bore 31
corresponding to the cylinder bore 31 shown in FIG. 5. The stepped
cylinder bore 31, which is formed in the first arm 13A, has a
cylinder chamber 31A and a smaller diameter axial bore 31B
connected to the cylinder chamber 31A. The lock pin 45 has a shaft
portion 46 slidably extending in the axial bore 31B. The cylinder
chamber 31A is hydraulically connected to the oil supply unit 50
(FIG. 1) through the oil passage 16 and the bore 20 of the cam
shaft 18, similar to FIG. 1.
The shaft portion 46 of the lock pin 45 can be disengageably
inserted in the recess 48 formed in the second arm 13B. The recess
48 is coaxial to the axial bore 31B in the locked position shown in
FIG. 6 and has the same diameter as that of the axial bore 31B. The
lock pin 45 is continuously biased toward the second arm 13B by the
spring 43 provided in the cylinder bore 31.
When the pressurized oil is supplied to the cylinder chamber 31A to
move the lock pin 45 to the right in FIG. 6, against the spring 43,
the shaft portion 46 of the lock pin 45 is disengaged from the
recess 48, so that the second arm 13B can rotate relative to the
first arm 13A about the shaft 15. Namely, the lock pin is brought
into the unlocked position when pressurized oil is supplied to the
cylinder chamber 31A, as shown in FIG. 8.
The numeral 67 designates a stop plate secured to the first arm 13A
to limit the rotational movement of the second arm 13B about the
shaft 15 in the reverse direction, i.e., in the counterclockwise
direction in FIG. 6.
According to the arrangement shown in FIGS. 6 to 8, since the
recess 48 formed in the second arm 13B and the axial bore 31B
formed in the first arm 13A are in alignment with each other in the
locked position shown in FIG. 6 and have the same diameter, and
since the cylinder bore 31 has the cylinder chamber 31A and the
smaller axial bore 31B, the recess 48, the axial bore 31B, and the
cylinder chamber 31A can be easily formed by drilling or machining
at one time from the side of the cylinder bore 31. Namely, in spite
of the fact that the recess and the cylinder bore are formed in the
respective separate members, i.e., the second and first arms,
respectively, the recess 48 and the cylinder bore 31 can be formed
at one time, and accordingly, centering need not be taken into
account, which centering would otherwise have to be precisely
effected. The cylinder bore 41 is covered by an end plate 56 after
the recess and the cylinder bore are formed.
According to the arrangement shown in FIGS. 6 to 8, since the
recess 48 and the cylinder bore 31 can be machined at one time, as
mentioned above, play between the lock pin 45 and the recess 48 can
be eliminated or at least reduced.
The elements in FIGS. 6 to 8 corresponding to those of the first
and second embodiments are designated by the same reference
numerals as those in FIGS. 1 to 5.
The operation of the apparatus shown in FIGS. 6 to 8 is
fundamentally identical to that of the first or second embodiment
mentioned above.
FIGS. 9 to 11 show still another embodiment of the present
invention.
In a variant illustrated in FIGS. 9 to 11, the lock pin 45 is
provided with an axial hole 90 extending therethrough. Namely, the
axial hole 90 opens at one end into a cylinder chamber 31C of the
cylinder 31, which in turn opens to the atmosphere, and at the
opposite end into the recess in which the shaft portion 46 of the
lock pin 45 can be disengageably engaged, as mentioned before. The
axial hole 90 serves as an air escape or air discharge hole through
which the air which otherwise would be confined in the recess 48,
and which could also provide a resistance against the movement of
the lock pin into the recess 48, can be discharged into the
atmosphere through the cylinder chamber 31C, when the lock pin 45
is forced into the recess 48. In this manner, the escape of the air
otherwise confined in the recess 48 into the atmosphere through the
axial hole 90 of the lock pin 45 ensures a smooth and quick
movement of the lock pin 45 from and into the recess 48. It will be
appreciated that if an air escape hole is not provided, the air
confined in the recess 48 can be reduced in pressure when the lock
pin 45 is quickly drawn out from the recess 48, resulting in a
resistance to a quick and smooth movement of the lock pin 45.
Namely, the axial hole 90 contributes to a smooth and quick
movement of the lock pin not only in the forward but also the
backward movement thereof.
The arrangement illustrated in FIGS. 9 to 11 is slightly different
from that of FIG. 6, in addition to the presence of the axial air
discharging hole in the lock pin 45. For example, in the
arrangement shown in FIGS. 9 to 11, two coil springs 29' are
provided on opposite sides of the first and second arms 13A and
13B; one end of each coil springs 29' is fitted in a corresponding
slit 59 provided in the second arm 13B; an additional spring
retainer 57 is provided on the end plate 56, which is in the form
of a snap ring in the illustrated embodiment; and, the contact
surface 36 of the first arm 13A is not curved but substantially
flat, whereas only a contact surface 37 of the second arm 13B is
arcuated. However, these differences have no significance in the
working of the present invention.
* * * * *